1. Field
The present invention relates to a method for separating semiconductor devices from a substrate using a nanoporous structure, and more particularly, to a method for separating semiconductor devices from a substrate using a nanoporous structure, wherein a surface metal layer is deposited after electrolytic etching in the absence of the surface metal layer and then a GaN thin film is transferred to a metal wafer by wafer bonding and lift-off processes.
2. Discussion of the Background
Currently, gallium nitride (GaN; Gallium Nitride) is typically used in fabrication of light emitting diodes (LED; Light-Emitting diodes). GaN is generally formed on a sapphire substrate, which is an electrically non-conductive material. In this case, however, there are problems such as increase in resistance due to horizontal transfer of current, increase in operating temperature of devices due to low thermal conductivity of the sapphire substrate, and the like. To resolve such problems, it has been studied to separate LED structures from a substrate and to transfer the LED structures to a conductive substrate having high thermal and electrical conductivity.
Particularly, a lift-off process for separating a thin GaN layer from a sapphire substrate plays a very important role in fabrication of a vertical type LED. Currently, although a laser lift-off (LLO) process is generally used in the art, this process has various problems such as high fabrication cost and low yield due to long process time and thermal damage during processing. Thus, various studies have been made to develop a chemical lift-off (CLO) process based on chemical etching in order to resolve such problems.
Chemical lift-off (CLO) can be realized in various ways. Particularly, Korean Patent Registration No. 10-1001782 (Title of the Invention: Method for separating semiconductor device from substrate) and Korean Patent Registration No. 10-1001773 (Title of the Invention: Method for selective etching of semiconductor region) also disclose techniques relating to chemical lift-off. However, in these techniques, when metal for wafer bonding is deposited onto a wafer, electrochemical reaction intensively occurs on the metal surface in the course of electrolytic etching, thereby causing significant deterioration in electrochemical etching properties on the surface of GaN.